1. Field of the Invention
The invention relates to X-ray tables and more particularly to tiltable tables
2. Description of the Prior Art
In so-called tilting type X-ray tables the table body is pivotally connected to a base or pedestal part so that it can be tilted in either direction from its normal position in which the patient-supporting surface is horizontal. This tilting permits a patient to be examined, in any angular table body position between two vertical positions. X-ray tables of this type are well known. Such a table typically includes a movable tower assembly which supports an X-ray tube within the body. The tower also supports radiation responsive devices, such as, a spot filmer, an image tube, and cameras for viewing the image tube output. These devices are usually above the patient supporting top of the table.
The tower assembly includes a column or tower within a forwardly extending portion that extends into the body of the table and underneath the top. This tower extension is mounted on carriage for movement horizontally in a direction transverse to the length of the table. The carriage is in turn supported on suitable ways in the body of the table for movement lengthwise of the table proper. The tower projects from the rear of the table body and supports a further carriage for movement towards and from the table proper. The further carriage carries the radiation detection device which is also movable throughout substantially the entire length of the table.
The movement of a tower assembly should be smooth and relatively effortless. It also should be linear to maintain accurate and consistent spatial relationship among a patient, the table's X-ray tube and the supported imaging devices. If the movement of the tower assembly and the table top is to be consistent and linear the table must be rigid and accurately manufactured.
Conventionally, tables have been constructed in which an upper frame and connected or integrally formed track elements supported the tower assembly. These track elements provided flat track surfaces which were in planes either parallel or perpendicular to the plane of the patient supporting surface.
The condition when smooth tower assembly movement is most difficult to achieve is when the table is tilted to .theta. vertical orientation. Since the tower carriage movement is vertical rather than horizontal, both the tower and counterweights of equal mass within the table must move vertically and easily. When the table is vertical the mass of the tower assembly, most of which is external of the table body, applies twisting forces to the tower assembly guide tracks and rollers. The resultant of these forces is a plane which is skewed with respect to the plane of the table top.
With prior tables, tower assembly rollers have been positioned such that some had their axes parallel to the table top while others had their axes perpendicular to the table top. Since the forces applied are skew with respect to the plane of the table top the forces applied to the rollers were not purely radial, but rather have significant axial vectors. This skewed force application caused the rollers to perform poorly and wear excessively.
Prior to the present invention various methods of constructions have been employed for supporting the column or tower in the table, but none are entirely satisfactory.